JPH06103263B2 - Two component type gas analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention adopts a unique non-conventional method called a multi-fluid modulation method (this is the name named by the present inventors). The present invention relates to a two-component measurement type gas analyzer capable of simultaneously obtaining the concentrations of two components to be measured in a sample gas while using only one detector.

The applicant of the present application has filed a patent application for the fluid analysis method using the multi-fluid modulation method on December 11, 1987.

[Conventional technology]

For example, as a conventional means for simultaneously measuring the concentrations of two measurement target components contained in a sample gas by an infrared gas analyzer, there are those shown in FIGS. 4 and 5, respectively.

That is, FIG. 4 shows a so-called single cell type, in which 41 is a cell, and the sample gas S and the comparison gas R are alternately supplied by the fluid modulation means 42 such as a rotary valve. There is. 43 is a light source for generating infrared rays.

44, 45, 46 are solid-state detectors arranged in parallel with each other, and are provided with solid-state filters 44F, 45F, 46F, respectively. Is configured as a CO measuring filter having an absorption band, and the solid-state filter 46F is configured as a comparison filter having an absorption band having a wavelength different from the absorption wavelength bands of the solid-state filters 44F and 45F. Incidentally, 4
Reference numerals 7, 48, 49 are amplifiers provided on the output side of the solid-state detectors 44, 45, 46.

Further, FIG. 5 shows a so-called double cell type, in which reference numerals 51 and 52 are a comparison cell and a measurement cell which are arranged in parallel with each other. Light source 5
3 and a reflection mirror 54 on the other end side. And
A solid filter 44 is provided between the reflecting mirror 54 and both cells 51, 52.
F, 45F, 46F solid state detectors 44, 45, 46 are arranged in parallel with each other, the measurement light passing through the cells 51, 52 is reflected by a reflection mirror 54 solid state filters 44F, 45F, The solid state detectors 44, 45 and 46 are reached via 46F.
Incidentally, 55 is a chopper for modulation.

[Problems to be solved by the invention]

However, in the devices shown in FIGS. 4 and 5, three detectors are required to measure two components to be measured, which complicates the structure and adjusts the sensitivity between the detectors. There are drawbacks such as that

The present invention has been made with the above matters in mind, and it is an object of the present invention to measure the concentrations of two components to be measured in spite of using only one detector. Moreover, it is to provide a useful two-component measurement type gas analyzer which does not require adjustment.

[Means for solving problems]

In order to achieve the above-mentioned object, a two-component measurement type absorption spectrometer according to the present invention is provided with two cells in parallel between a light source and a detector, and each cell has a characteristic absorption wavelength of a measurement target component. A filter having an absorption band at substantially the same wavelength is provided, and one fluid modulation means is provided for each cell to switch and supply the sample gas and the reference gas simultaneously and continuously in a fixed cycle. Are provided respectively so that the modulation frequencies of the sample gas and the reference gas by these two fluid modulation means are different from each other, and the output signal from the detector is separated into signal components of each modulation frequency for each cell and rectified respectively. And smoothed.

[Action]

According to the above configuration, an output signal in a state in which two signal components corresponding to each cell are superposed is output from one detector provided in common to the two cells. And
Since these two signal components are modulated at different frequencies, by separating the output signal from the detector into signal components of each modulation frequency for each cell and rectifying and smoothing them respectively, A signal corresponding to the concentration, that is to say the concentration of the two components to be measured, can be obtained, and the above object is perfectly achieved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an infrared gas analyzer for simultaneously measuring CO and CO ₂ as components to be measured, where 1, 2 are cells arranged in parallel with each other, 3, 4 are cells 1, 2 It is a light source for irradiating infrared rays.

Reference numeral 5 denotes a solid-state detector as a detector, which is a cell of a body 5A having two light guide paths, for example, which are mirror-finished inside thereof.
On the side facing the body 2, solid filters 5a and 5b are provided so as to correspond to the cells 1 and 2, and at the position on the other end side of the body 5A where the light passing through the light guide path is incident, solid detection element
5c is provided. Then, the one solid filter 5a is configured as a CO measurement filter having an absorption band at a wavelength substantially the same as the characteristic absorption wavelength of CO, and the other solid filter 5b is
CO ₂ having an absorption band at a wavelength approximately the same as the characteristic absorption wavelength of CO ₂
It is configured as a measurement filter. 6 is this detector 5
Is a preamplifier provided on the output side of the.

Reference numerals 7 and 8 denote fluid modulation means for supplying the sample gas S and the reference gas R to the cells 1 and 2 at the same time and continuously in a fixed cycle, and are constituted by rotary valves, for example. The modulation frequencies of the sample gas S and the reference gas R by the fluid modulation means 7 and 8 are different from each other. For example, the modulation frequency of the fluid modulation means 7 is 1 hertz and that of the fluid modulation means 8 is 2 Hz. Hertz. Therefore,
When the sample gas S and the reference gas R are supplied to the cells 1 and 2 by the fluid modulation means 7 and 8 having the above-mentioned modulation frequency, the detector 5 outputs the signal in the band near the modulation frequency and the cell 2 from the detector 5. An output signal A in which a signal in a band near the modulation frequency is superimposed is output.

Reference numeral 10 is a signal processing means connected to the output side of the detector 5 via the preamplifier 6, and its specific configuration is, as shown in FIG. 2, an output signal from the detector 5 input via the preamplifier 6. A is divided into two signal processing sequences and processed.

That is, one signal processing sequence is provided with a bandpass filter 11 for separating and extracting (passing) only the signal (for example, a) in the band near the modulation frequency (1 hertz) for the cell 1, and the subsequent stage. In addition, due to the synchronization signal from the synchronization signal generator 7a attached to the fluid modulation means 7 for the cell 1 (the signal representing the actual fluid modulation operation by the fluid modulation means 7: Hertz), the bandpass filter 11 alone is insufficient. A bandpass filter 11 is provided so that a more accurate detection can be performed by supplementing a possible separation action, and at the same time, the separated AC can be converted (rectified) into DC.
The synchronous detection rectifier circuit 13 for synchronously rectifying the output signal a from the synchronous detection rectification circuit 13 is provided, and the synchronous detection rectification circuit 13 is further provided at the subsequent stage.
Is provided with a low-pass filter as an example of a smoothing circuit 15 for smoothing the output signal a from the device and removing high frequency noise, and the other signal processing sequence modulates the fluid modulation means 8 for the cell 2. Frequency (2 hertz)
A bandpass filter 12 for separating and extracting only a signal (for example, b) in a nearby band is provided, and a synchronization signal from a synchronization signal generator 8a attached to the fluid modulation means 8 for the cell 2 is provided at the subsequent stage ( The signal that represents the actual fluid modulation operation by the fluid modulation signal 8: 2 Hertz) can supplement the separation action that may be insufficient with the bandpass filter 12 alone to perform more accurate detection and at the same time A synchronous detection rectifier circuit 14 for synchronously rectifying the output signal b from the bandpass filter 12 is provided so that the generated alternating current can be converted into direct current, and further the output signal from the synchronous detection rectifier circuit 14 is provided at the subsequent stage. A low-pass filter is provided as an example of a smoothing circuit 16 for smoothing b and removing high frequency noise. From this signal processing means 10, cells 1 and 2 are connected. a as a signal component of response
And b are output independently of each other.

The signal processing means 10 is not limited to hardware means such as the above electric circuit, but Fourier analysis (corresponding to frequency separation processing) and absolute value averaging processing (corresponding to rectification / smoothing processing), etc. It is also possible to employ software-like means such as a computer system capable of performing the arithmetic processing of the numerical analysis.

Thus, in the two-component measurement type gas analyzer having the above configuration,
The sample gas S and the comparison gas R by the fluid modulation means 7 and 8
And 2 are simultaneously and continuously supplied to the cells 1 and 2 at modulation frequencies of 1 hertz and 2 hertz, respectively, one detector 5 provided in common to the two cells 1 and 2 is
And the signal component corresponding to the cell 2 (the signal component corresponding to the measurement target component CO: a) and the signal component corresponding to the cell 2 (the measurement target component CO
₂ outputs the output signal A in which the signal component: b) commensurate with ₂ is superimposed, and since both signal components a and b are modulated at different frequencies, the output signal A from the detector 5 is output to each cell 1 , 2
By separating and rectifying and smoothing the signal components a and b of each modulation frequency for
The signals a and b respectively corresponding to CO ₂ can be obtained, so that the concentrations of the _two measurement target components CO and CO ₂ can be obtained, respectively.

FIG. 3 shows another embodiment of the present invention. In FIG. 3, reference numeral 20 is a condenser microphone type detector, and its light receiving chambers 20a and 20b are arranged so as to correspond to cells 1 and 2, respectively, and Solid filters 21a and 21b are arranged between the cells 1 and 2 and the light receiving chambers 20a and 20b, respectively. Here, the solid-state filters 21a and 21b are respectively configured similarly to the solid-state filters 5a and 5b in the above-mentioned embodiment. Further, CO and CO ₂ are enclosed in the light receiving chambers 20a and 20b. Incidentally, in FIG. 3, the fluid modulation means 7, 8 are omitted. 2 configured in this way
The function and effect of the component measuring gas analyzer are the same as those of the above-mentioned embodiment, and therefore the description thereof is omitted.

The present invention is not limited to the above embodiment, but can be applied to other gas analyzers such as an ultraviolet gas analyzer. The fluid modulation means may be composed of a 4-way switching solenoid valve, a 3-way switching solenoid valve, or the like. Also solid filters
A gas filter may be used instead of 5a, 5b, 21a, 21b.

〔The invention's effect〕

As described above, in the two-component measurement type gas analyzer according to the present invention, two cells are provided in parallel with each other between the light source and the detector, and each cell has substantially the same characteristic absorption wavelength as the measurement target component. With a filter having an absorption band at the wavelength, a sample gas and a reference gas for each cell,
The above-mentioned detection is performed by providing one fluid modulation means for each cell at the same time and continuously in a fixed cycle so that the modulation frequencies of the sample gas and the comparison gas by these two fluid modulation means are different from each other. Since the output signal from the detector is separated into the signal components of each modulation frequency for each cell and rectified and smoothed respectively, no adjustment work is required in spite of using only one detector. It is possible to measure the concentrations of the two components to be measured simultaneously without requiring.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a two-component measurement type gas analyzer according to the present invention, and FIG. 2 is a block diagram showing an example of signal processing means. FIG. 3 is a block diagram of the essential parts showing another embodiment of the present invention. 4 and 5 are explanatory views showing a conventional technique. 1,2 ... cell, 3,4 ... light source, 5,20 ... detector, 5a, 5b, 21a, 21b
... filter, 7, 8 ... fluid modulation means, a, b ... signal component, S ...
Sample gas, R ... Comparative gas

Claims (1)

[Claims] 1. Two cells are provided in parallel with each other between a light source and a detector, each cell is provided with a filter having an absorption band at a wavelength substantially the same as a characteristic absorption wavelength of a component to be measured, and each cell is provided. On the other hand, a fluid modulation means for switching and supplying the sample gas and the comparison gas simultaneously and continuously at a constant cycle is provided for each of the cells.
The modulation frequencies of the sample gas and the reference gas by the two fluid modulation means are made different from each other, and the output signal from the detector is separated into signal components of the modulation frequencies for the cells and rectified and smoothed respectively. A two-component measurement type gas analyzer characterized in that